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United States Patent |
5,352,509
|
Talling
|
October 4, 1994
|
Insulating product of mineral fibre wool, intended in particular for
heat insulation of pipes and method for preparing this product
Abstract
The invention relates to a heat insulation product of mineral fiber wool.
The curable binding agent of the product is an aqueous suspension
containing water glass and slag. The slag reacts hydraulically with the
alkalis or the water glass yielding water resistant bonds. During the
preparation of the product, the suspension of water glass and slag is
agitated before being applied onto the product. The curing of tile binding
agent can be carried out immediately or at a later time. Curing may be
effected at room temperature or at an elevated temperature.
Inventors:
|
Talling; Bob L. O. (Abo, FI)
|
Assignee:
|
Oy Partek AB (Pargas, FI)
|
Appl. No.:
|
179762 |
Filed:
|
January 10, 1994 |
Foreign Application Priority Data
Current U.S. Class: |
442/327; 106/624 |
Intern'l Class: |
D04H 001/58 |
Field of Search: |
428/288,289,311.5
106/624
|
References Cited
U.S. Patent Documents
3002857 | Oct., 1961 | Stalego | 427/126.
|
4018616 | Apr., 1977 | Sugahara et al. | 106/629.
|
4427356 | Jan., 1984 | Kratel et al. | 428/195.
|
4985163 | Jan., 1991 | Kratel et al. | 252/62.
|
Foreign Patent Documents |
2804069A1 | Aug., 1979 | DE | .
|
7513183-9 | Feb., 1981 | SE | .
|
7514229-9 | Oct., 1981 | SE | .
|
Other References
Derwent's Abstract No. 38 399 B/20, SU 614 061, publ. week 7920 (Dnepr Eng
Cons Inst).
|
Primary Examiner: Lesmes; George F.
Assistant Examiner: Raimund; Christopher W.
Attorney, Agent or Firm: Dressler, Goldsmith, Shore & Milnamow, Ltd.
Parent Case Text
This application is a continuation of application Ser. No. 768,313, filed
Jan. 6, 1992, now abandoned.
Claims
I claim:
1. Insulating product of mineral fibres intended in particular for the heat
insulation of pipes whereas its binder consists essentially of water glass
and slag, the water glass having a molar ration R.sub.s of 2.3 to 3.0, in
which product the weight ratio of the mineral fibre amount to the dry
substance of the water glass is 100:1-100:20, the slag is present in the
binder in such an amount that the weight ratio of the dry substance of the
water glass to the slag is 100:1-100:50, and the slag is pulverized blast
furnace slag.
2. Insulating product according to claim 1, whereas the binder is present
in the product in such an amount, that the weight ratio of the mineral
fibre amount to he dry substance of water glass is 100:5-100:14.
3. Insulating product according to claims 1 or 2, whereas the slag is
presenting the binder in such an amount that the weight ratio of the dry
substance of the water glass to the slag is 10:1-10:2.
4. Insulating product according to claims 1 or 2, whereas the binder
contains dust binding, hydrophobizing or additional curing agents for the
mineral fibres.
5. Insulating product according to claims 1 or 2, whereas it is uncured and
packed in a moisture- and gasproof package.
6. Insulating product according to claim 1 or 2, whereas the binder
consists essentially of water glass and slag, the water glass having a
molar ratio R.sub.s of 2.7-3.0.
7. Insulating product according to claims 1 or 2, whereas the binder
contains dust binding, hydrophobizing and additional curing agents for the
mineral fibres.
8. Insulating product according to claim 7, whereas the binding agent is
polybutene and the hydrophobizing agent is silane.
Description
The present invention relates to an insulating product of mineral fibres
intended in particular for the heat insulation of pipes. The product shall
have a good temperature resistance, moisture resistance and a strength
that resists a high temporary load, e.g. the steps of the pipe fitter on
the pipe during installation operations. The insulating product shall be
shapeable at once or later to the desired shape and subsequently curable
at the prevailing outer temperature or at a raised temperature.
In view of an economically optimal production of the product, the
production shall be feasible in a conventional installation for the
production of mineral wool webs. The curing temperature shall be adaptabe
to the circumstances and the curing time shall be short.
The Finnish patent specification 67751 discloses the production of
insulating bodies based on mineral wool. In order to achieve the desired
compression resistance and temperature resistance, clay sludge, preferably
bentonite, is absorbed by means of under-pressure into a preshaped and
cured tubular bowl or insulating plate. The process requires a curing of
several hours in a furnace. The insulating body has a good temperature
resistance, of at least 800.degree. C., but is expensive owing to a slow
and costly production process and expensive raw material. An additional
drawback of the bentonite body is its coarse surface, requiring an
additional surface treatment, i.e. milling, thus increasing the price of
the material.
Phenol cured insulating bodies are also known. Phenol is a fairly cheap and
rapidly curing binder. A phenol cured product resists temperatures of up
to 250.degree. C., but if the temperature is above 250.degree. C. for a
long period of time, the bonds are destroyed. At higher temperatures, of
400.degree. C. and more, the binder residues flare up, the temperature
rises rapidly and the product collapses. Another drawback of phenol
insulating bodies consists in their emitting poisonous gases during
burning.
The SE lay-out print 420 488, for instance, discloses the use of a mass
based on water glass and clay mineral substances as a binding agent. The
binder provides a good water and heat resistance in the product. On the
other hand, the product has a poor compression resistance, meaning that
e.g. a tubular bowl made of mineral fibres and treated according to the
layout print does not resist temporary load. Moreover, the product is
brittle and thus causes dusting.
According to the present invention, it has been noted that an insulating
product can be achieved, which is especially suitable as a tubular bowl,
out of a mineral fibre web prepared in a conventional manner by using as a
binding agent a water glass based binder with an addition of slag.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the temperature rise on the fire side of a sheet product
according to the present invention tested according to SFS 4193.
FIG. 2 shows a typical relation between the splitting resistance and the
density of a sheet product according to the present invention.
FIG. 3 shows the relation between the tensile bending strength and the
density of a number of sheet products according to the present invention.
FIG. 4 shows the force required for compressing a cured sheet product
according to the invention 5 and 10% respectively.
The slag imparts many valuable properties to the insulating material. The
alkalis of the water glass act as activators of the slag (cf. slag alkali
cement). Together with water glass, slag forms a hydraulic bond giving the
cured product an improved compression resistance, a reduced brittleness
and thus reduced dusting and grater dust particles, compared to products
treated with binders containing water glass without a slag addition.
Moreover, a good temperature resistance is achieved in a product containing
a binder based on water glass and having a slag addition. Due to the
hydraulic bond of the slag to the water glass, the water is firmly bound,
chemically bound to the structure. The chemically bound water increases
the fire-resistance capacity of the material in that the water evaporating
at a fire temperature keeps down the temperature for a longer period. A
water glass based binder resists a longlasting temperature charge of up to
800.degree. C.
Combined with the water glass, the slag increases the crystallinity of the
material, thus reducing the moisture absorption tendency and the moisture
sensitivity.
Moreover, a more rapid curing and the possibility of optional curing
conditions are provided. The curing time for a product containing water
glass and slag in the binder and by using conventional curing in a curing
chamber is approx. 20-60 seconds for thin products and approx. 20 min. at
the most for thick tubular bowls. Equally good curing times are achieved
with phenol containing binders, but these binders are unsuitable in other
respects. Other known binders require curing times of up to several hours.
Another advantage of the system water glass/slag is that the binder enables
the forming of no-swelling compounds, although the temperature exceeds the
swelling temperature of pure water glass, 160.degree. C.
Further advantages of the slag is its reactivity at a normal temperature.
This means among others that the slag totally prevents carbonation, which
is a noticeable advantage. Other mineral curing agents, like fly ash and
clay, do not possess this property. Clay and corresponding substances
mainly act as fillers.
It has been noted according to the invention, that the advantageous effects
of slag are achieved with relatively small amounts of slag, both with
regard to the amount of water glass and to the amount of fibres. In the
binder, the weight ratio of the dry substance of the water glass to the
slag can be approx. 100:1-100:50, prefrably 10:1-10:2. In the product, the
weight ratio of the mineral fibre amount to the dry substance of the water
glass can be approx. 100:1-100:20, preferably 100:5-100:15.
The slag of the binder is preferably blast furnace slag.
The slag/water glass system is well controllable and thus provides a geat
flexiblity for the method of preparing an insulating product of mineral
wool. Controllable components are among others:
______________________________________
slag water glass (VG)
curing conditions
______________________________________
slag chemistry
type of VG temperature
slag mineralogy
molar ratio time
grinding fineness
modifier environment
(moisture)
particle distribution
VG compositions
modifier
slag amount
______________________________________
Knowledge of the behaviour of various slags in an alkaline environment
enables the control of the properties of the final product.
The slag reacts with the alkalis of the water glass, i.e. it is activated.
Thus, water resistant hydrate phases of a zeolite type are obtained. Owing
to this mechanism, the molar ratio R.sub.s (the ratio of the silicon moles
to the alkali moles in the water glass) for the residual unreacted water
glass rises so much that also this residue becomes water resistant. A
higher alkali content, i.e. a lower molar ratio R.sub.s, requires a higher
slag portion in order to tie up the alkalis in a water resistant form.
The molar ratio R.sub.s of commercial water glass is approx. 3.3. According
to the invention, it has been observed that very low molar ratios are also
usable, requiring in that case high slag contents in order to provide
water resistance of the final composite. Even NaOH or Na.sub.2 CO.sub.3
are usabe. However, it is preferable to use the molar ratio R.sub.s
.gtoreq.2.3. The optimal moisture resistance with regard to the reactivity
with slag is obtained for R.sub.s =2.7-3.0.
The main components of the slag-glass are CaO, MgO, SiO.sub.2, Al.sub.2
O.sub.3. It is generally true about slag/water glass systems that the
lower the CaO content, i.e. the ratio CaO/SiO.sub.2, the lower a molar
ratio R.sub.s should be used in order to obtain a hydraulic bond within a
reasonable period of time. When using low molar ratios, R.sub.s
.ltoreq.2.7, the slag content has to be increased. With a higher ratio
CaO/SiO.sub.2 .gtoreq.1.3, water glass can be used with R.sub.s
.gtoreq.3.3 , still obtaining a sufficient reactivity.
The reaction degree is controlled by means of the temperature and the
curing time. A higher curing temperature shortens the curing time and vice
versa.
A lower R.sub.s shortens the curing time at a constant temperature. A
higher R.sub.s requires a longer curing time or a higher temperature.
By prereacting slag with water glass at a normal or a raised temperature
under agitation, the reaction degree and the curing rate can be further
increased. A finished hydrate phase is consequently created, speeding up
the curing when the binder has been applied onto the mineral wool.
In case the curing temperature exceeds approx. 160.degree. C., the slag
content has to be increased in order to prevent the water glass from
swelling (cf. slag alkali cement).
Trituration of the slag increases the reaction rate and the reactivity.
This enables to use a water glass with a higher R.sub.s, or optionally a
very rapid curing can be ahieved at a lower R.sub.s. A finely ground slag
also improves the stability of the slurry of water glass and slag.
The water glass can be a sodium, potassium, lithium or ammonium silicate
solution. In case the slag content is high, hydroxides and/or carbonates
can be added.
The preparation of a mineral wool product and the addition of the binder
based on water glass and containing slag takes place conventionally in a
conventional set of apparatus. The binder is added as a solution through a
nozzle to the fibres in the wool chamber of a conventional machine line.
The water glass and the slag are premixed in water and are kept in
agitation before the distribution on the wool. The curing of the binder
mixed wool material takes place at once or later, at room temperature or
at a raised temperature.
Besides water glass and slag, the binder solution can contain possible
additional curing, modifying, dust binding and/or hydrophobing agents.
The spraying of the binder solution and the additives takes place directly
after the fibre formation, preferably in the wool chamber. This is an
essential advantage, since the wool is in a virginal state here and thus
has a good adhesiveness.
The binder composition is sprayed on the wool through the binder nozzles of
the centrifuge, both peripheral and central sprayers being then usable.
Optionally two different solutions can be fed into the wool, so that
possible modifying and/or additional curing agents are fed through the one
sprayer and a slurry of water glass/slag+possible modifying agents through
the other sprayer.
An additional binder solution can appropriately be added to the wool in a
subsequent step of the production of the insulating material. By applying
more binder solution on the primary web, a composite having a better
resistance is achieved. By adding additional additives on the primary web
special properties can be given to the material.
Before the feeding of the binder only compatible substances need to be
premixed, whereas the other necessary additional components are mixed only
at the moment of application. The mixing can be carried out for istance by
rapid mixing, e.g. in tubular mixers. Thus the dwell time will be short
enough not to allow any gelling or precipitating reactions to take place.
The required additional water is also adjusted by feeding into the rapid
mixer. The water amount is adjusted so as to provide the correct moisture
for the primary web and prevent dusting. The water evaporation taking
place in the wool chamber increases the viscosity of the fibre composition
applied onto the fibre. The high viscosity means a very low ion migration,
thus decreasing the reaction rate. In this manner, the primary web retains
its elasticity and curability for several days/weeks, provided that
further water discharge is prevented.
When producing insulating sheets, these are appropriately cut out from a
mineral web, which has been conventionally laid out by oscillating to the
desired thickness and then cured.
According to a preferred method, the mineral fibre web is cured at room
temperature, for instance between metal sheets. Thus the sheet will
acquire a better flexibility. A slowly cured fibre body is, as is known,
more flexible, elastic, than a fibre body that has to be cured at a high
temperature.
According to another preferred embodiment a secondary web having the
desired thickness is taken up in an uncured state and stored in a non
curing environment, e.g. enclosed in plastic at a suitable temperature and
during a determined time at the most. This insulating material is used in
situ for the insulation in places that are not easily accessable and have
an awkward shape, such as for instance renovation objects. Afterwards, the
insulation cures at the prevailing temperature. It is relatively easy to
apply an insulating mat having a suitable thickness onto or around various
bodies difficult to access. The curing does not require any special
measures or equipment since it takes place spontaneously at the prevailing
temperature.
The method is also suitable for blow wool applications, in which uncured
fibre material torn into small tufts is applied onto pipes, where the wool
can be cured at the prevailing temperature.
When producing tubular bowls, a secondary web is shaped to the desired
shape of a tubular bowl, and is subsequently cured in a known manner. The
curing can take place rapdily at a high temperature or slower at a lower
temperature.
Additional additives, like additional curing, modifying, dust binding and
hydrophobizing agents cooperate with the water glass/slag system.
According to the invention, the additional curing agents consist of mineral
salts and compounds, suitable acids, esters or alcohols or of combinations
of these. The mineral salts can be e.g. magnesium, aluminium or calcium
salts or compounds. Phosphoric acid, for instance, is a usable acid.
Buffer curing agents can also be used for adjusting the storage time. The
additional curing agent may be a combination of the above mentioned curing
agents.
For the water glass, various modifying agents like organic and unorganic
polymers, cellulose and silicones like silicon organic polymers are
appropriately used. Also monomers polymerized by e.g. a pH change or a
temperature rise during the curing can be used. The modifying agents of
water glass have in common the fact of not being film forming. By means of
the modifying agents one aims at softening the water glass, thus
increasing its adhesiveness to the fibre surface.
The water glass modifier improves the elastic properties, the water
resistance, carbonation resistance etc. of the water glass.
As dust binding agents, alcohols, polyols, film forming polymers, gelling
polymers, waxes, oils, fats, paraffines etc. are appropriately used. The
task of the dust binding agent is to bind together the dust or to bind it
to the main matrice either physically (film forming) or chemically
(surface active properties). In case high temperature curing is used,
melting dust binding agents, e.g. stearates, can be used, or curing dust
binders, forming a film over the matrice. A great number of the dust
binding agents simultaneously have a water repellent effect.
The task of the hydrophobizing agent is to prevent water and moisture from
penetrating into the product. As hydrophobizing agents, silanes,
silicones, oils, various hydrophobic compounds and hydrophobic starch are
used. It is essential that possible hydrophilic emulgators are
destroyable, which happens by raising the pH value or by a temperature
raise.
The polybutene silane compound has proved especially advantageous as a dust
binding agent and a hydrophobing agent. The polybutene acts as a dust
binder and the silane as a hydrophobing agent.
Within the various groups, compatible compounds can be mixed in advance,
whereas non compatible compounds have to be mixed immediately before the
application or applied through separate nozzles.
The invention is explained below by means of various examples and
indicating the values of various essential properties of the produced
insulating products.
Example 1
A suspension of 83% of water glass (R.sub.s =2.7, dry content 39%) and 13%
of blast furnace slag were mixed with a modifying solution (dry content
8%), containing silane as a hydrophobing agent and polybutene as a film
forming dust binder, in a tubular mixer. Calculated as dry substance, the
water glass forms 11.2% of the wool, the slag 13% of the water glass and
the modifiers 1.8% of the water glass. The wool production was 2.8 tons/h
and the dosing of the various solutions was 10.2 l/min or water
glass-slag-suspension, 3.2 l/min of modyfier solution as well as water 10
I/min. The primary web was rolled into a tubular bowl having a diametre of
350 mm and a wall thickness of 60 mm and the tubular bowl was cured at
145.degree. C. for 3 min. A piece 63.5 x 63.5 mm was cut out from the
tubular bowl and was tested with regard to linear shrinking at 600.degree.
C. according to ASTM 356-60. The shrinking was only 1.4% when the density
of the product was 101 kg/m.sup.3.
Example 2
A suspension of 95% of water glass (R.sub.s =3.3, dry content 37%) and 5%
of blast furnace slag were mixed with an additional curing agent (5%
H.sub.3 PO.sub.4) and a modifier solution (dry content 5%), containing a
hydrophobizing agent and a film forming polymer as a dust binder, in a
tubular mixer. Calculated as dry substance, the water glass forms 11.4% of
the wool, the slag 5%, the phosphoric acid 2.5% and the modifiers 0.8% of
the water glass. The wool production was 3.2 tons/h and the dosing of the
various solutions was 12.5 1/min of the water glass/slag-suspension, 5.3
1/min of the additional curer, 4.2 1/min of the modifier solution as well
as water 11 1/min. Out of the primary web, a sheet web was prepared in a
curing chamber at 140.degree. C. Fire tests according to SFS 4193 were
carried out on sheets having a thickness of only 26 mm and a density of
217 and 225 kg/m.sub.3 respectively, yielding a fire resistance of 52 and
58 min. respectively. The temperature rise on the fire side according to
SFS 4193 appears from FIG. 1 and table 1. The test was continued for one
hour and the temperature was 925.degree. C. at the end of the test. The
sheet was totally undeformed and unbent and the burnt area still had a
high residual strength.
It should be observed that the results given in the figures do not by any
means indicate the upper limits, but only typical values that can be
obtained. The results are collected from 11 different full-scale runs
testing more than 70 different formulas.
FIG. 2 shows a typical relation between the splitting resistance and the
density of a sheet product according to the invention.
FIG. 3 shows the relation between the tensile bending strength and the
density of a number of sheet products according to the invention.
The force required for compressing a cured sheet product according to the
invention 5 and 10% respectively is indicated in FIG. 4. The force is
given as kN/m.sup.2 as a function of the density.
Water absorption was tested according to BS2972:1975. The water absorption
of sheet products aiming at a good hydrophobicity was:
______________________________________
After an immersion of 0.5 hours, only 0.3-1.6% by volume
After an immersion of 1 hour, only 0.6-2.4% by volume
After an immersion of 2 hours, only 1.1-3.0% by volume
After an immersion of 1 day only 3.8-7.0% by volume
After an immersion of 7 days only 9.1% by volume
______________________________________
The moisture resistance was tested in a climatic chamber by measuring the
swelling during storage at 40.degree. C. and 95% relative moisture. The
temperature was selected as 40.degree. C. in order to obtain accelerated
results, since swelling at 20.degree.-30 .degree. C. is practically none
or very slow. The optimal results with a sheet product having a density of
140 kg/m.sup.3 showed no swelling after 1 day and only a swelling of 0.3%
after 7 days.
TABLE 1
______________________________________
Temperature rise as a function of time
Time t Temperature rise of the furnace T--T.degree.
min .degree.C.
______________________________________
5 556
10 659
15 718
30 821
60 925
90 986
120 1029
180 1090
240 1133
360 1193
______________________________________
Example 3
A suspension of 82% water glass (R.sub.s =2.4, dry matter content 44%) and
18% blast furnace slag were mixed with a modifier solution (dry content
10%), containing a hydrophobizing agent and a film forming polymer as a
dust binding agent, in a tubular mixer. Calculated as a dry substance, the
water glass represents 15.8% of the wool, the slag 50% of the water glass
and the modifiers 3.6% of the water glass. The wool production was 2.8
tons/h and the dosing of the various solutions was 13.2 1/min of water
glass/slag-suspension, 6.0 1/min of modifier solution and water 8 1/min.
Out of the primary web, tubular bowls were prepared, having an outer
diametre of 520 mm, a thickness of 120 mm and a density of 96.0
kg/m.sup.3. The bowls were mounted on a steam pipe, whose temperature was
raised up to 520.degree. C. After 60 hours at this temperature the
insulation was inspected and its .lambda. value was determined. The
.lambda. value was: 0.1010 W/m .degree. C. at 520.degree. C. The bowls
resisted the temperature (520.degree. C.) well. The only remarkable
difference was that the inner surface of the bowl had become harder than
the outer surface, probably due to the continued curing of the binder.
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